Car idles like a diesel (carbed)

[crazypete]

The problem started two weeks ago. I was driving around and it just lost power in the middle of a turn and it was kicking/intermittent power/cutting in-out for a few minutes beforehand. I sprayed some carb cleaner and it came back to life. I dropped in 4 bottles of fuel system cleaner and thought that was the end of that. This past saturday, it simply didnt want to start. I carb cleanered it again and then it kicked in. I drove cross state no problem. Stopped, started, no problem. That morning, the car started up but got worse and worse through the day. The air/fluel mixture guage bottoms out whenever I go down a hill/nosedown, clears out shortly after when I go level (but still feels like power is fluctuating when I have the pedal in just a bit off idle). Going uphill fixes all problems. If I punch it, the problem clears out. The floats are set right on since that was my first thought.

Ok, I get home and notice the temp needle is in the red! I stop and I hear EEEEEEEE as steam is pressing through a gasket up near the thermostat elbow. I popped the radiator open so my seals wouldnt all blow. I filled the oil-free radiator back up, changed the oil (which was clean oily oil with no coolant). I CRAZY carb cleanered it. I put carb cleaner into the fuel bowl too (I found this always helps). I sprayed around the carb base but no rpm spikes.

I start it and it sounds like a diesel. Sounds like it's running on not 7 but 6 cylinders, very lopey and stalls after a few minutes. The mixture was full rich then it fell to halfway soon thereafter. I hear doof doof from the exhaust and an awful lot of water coming from the tailpipes but no white smoke or smell. It revs fine (with a little hesitation) and the power is all there (I did a burnout) but then it starts "dieseling" again when I go back to idle. Arg!

Any ideas? Time for a new carb or blown coolant->cyclinder gasket? It would seem like the idle circuit is clogged somehow but carb cleaner in the fuel bowl should unclog it right? I must have done that 5-6 times by now.

[BLACK85GT]

I have had a similar problem before. It was my carb studs came loose. Also check/replace the carb to intake gasket.
If you are sucking air thru the base it could cause an overheat condition. Also check all the carb body bolts make shure everything is tight, they come loose sometimes.(remove carb for this there are some undertneath).

[crazypete]

Sure sounds like it's a vacuum leak. I'll attach a guage and check.

Here's a question: If I spray carb cleaner into the carb throat, is it supposed to bubble out from around the throttle shaft? I CC'ed it when the motor was hot and I saw it bubbling out from around the carb base and the throttle shaft on the passenger side of the carb (where the choke's arm attaches to, opposite the throttle arms).

The carb is still fairly new (<2 years) and has less than 6k miles on it.

Trouble is I semi stripped one of the carb studs so I cannot really clamp down on it. The other 3 are fine. What can be done? I was thinking to crazyglue gel the threads and permanently put that one stud in. I've tried plasteel but it is not effective.

[BLACK85GT]

The carb studs should be replaceable? Dont they screw into the intake? you should be able to just replace it with a new carb stud found in parts stores (they usually come in sets of 4).

Not shure about the other air bubbles, but if you have a loose stud, thats not good cause it could leak. They all have to be tight.
I dont think glue will hold it. It has to torque down.

[crazypete]

Actually, it was the aluminum intake that got stripped and not the stud. Sorry about being a bit vague. I'll seal the base today and I'll see if that helps it.

[bmxmon]

You might be able to drill the stripped stud hole out, re-tap it and put in a steel insert, then use a regular stud.

[crazypete]

So you good folks were right, half the studs were just hanging there. The carb must tip a bit under hard turns and break the seal just enough to stall out the motor.

I did noticed that my carb spacer to intake seal, which was done with rtv instead of a gasket was _solid_. I had to pry the spacer off with a screwdriver, it was sealed so well. So I was thinking that I never use the pcv or egr pasages under the carb for anything anyway, so I could rtv the carb carefully to the spacer and then rtv the spacer to the intake and then add the studs for show.

I've not had much success with taps or drilling out broken bolts. For aluminum, I usually get a bolt that has slightly bigger threads but a good taper. I then force it into place with a 2 foot breaker bar...effectivly brute force retapping the hole.

So my head swap has balooned into a carb rebuild, intake porting and head porting. I also learned that gas melts the goo stuck to pistons (also gives one a mad headache).

[BLACK85GT]

hopefully the rtv wont break of and get caught up in the carb passages. In a situation like this, I usually just replace the intake with a newer one that I wanted anyways.

[88fivepointoh]

I have learned never use RTV on the carb.. expensive experience.. Clogged the entire deal right up.. Big problems. anyways, I would replace the intake.. like everyone said, excuse to upgrade!

[crazypete]

But the rtv is below the carb...it would have had to travel against the motion of the vacuum to get to the carb.

I had an edelbrock performer that I am porting up right now that I am quite fond of. I think it already is one of the best carbed street low-midband range intake so replacing it would be rather fruitless.

On further examination, I think air was also seeping in past this stripped stud...

This car is gonna run like a champ when I put her back together!

Question, should such a vacuum leak cause a drop in intake vacuum? The vacuum guage looked like a solid 20-21 before I had removed it.

[rwhite65]

just heli-coil that thing I have had many dirt bikes over the years. Everything is aluminum on them, and I have stripped out just about all that can be. If the carb is off...just stuff a rag in the intake, drill it out, tap it....and hopefully the car will run like a champ...and not be RTV'ed down. The RTV might work ok, but I just think that is a bad idea. Just my $.02
Ryan

[~The Jester~]

I've NEVER had any luck with the RTV carb seal thing. Spend the few dollars and get the Mr. Gasket carb gasket, be done.

On your stripped threads, try a metric bolt that's a bit bigger than the 1/4 X 20 threads. I'm guessing 8mm??? Usually these have pretty aggressive threads, some even self tappers. Use the "Go in 2 turns, back out 1" method when installing. Usually does the trick, if not I like heli-coils.